This gets rid of the awkward checking-in of `template.html` to git (when
it's a built file) and also makes the rebuilds faster and more
consistent by running everything through the same pipeline. So inline
CSS, SVG, and JS are all partially built on-the-fly.
I've basically reinvented gulp, but it's pretty lightweight and
zero-dep, so I'm happy with it.
Nolan Lawson